Large generators have journal bearings often lubricated by oil rings, which rest on the top of the shaft. As the shaft rotates so does the oil ring to bring oil from a reservoir disposed under the journal bearing to the top of the shaft to lubricate the bearing. There is clearance between the journal bearing and the shaft so that as the shaft rotates a wedge of lubricating oil builds between the shaft and journal bearing floating the shaft on the wedge of oil. When generators are installed on a ship or large boat the pitch and roll upsets the action of the oil ring and may interrupt the flow of oil to the bearings. To prevent this, pressurized oil is supplied to the bearing. Also larger thrust bearings normally require that they be supplied with pressurized oil. To provide a fail safe lubricating oil supply from an oil pump, the oil pump should be driven by the generator.